Most every Mamoru Hosoda film has been about, not just a family, but Family. Mirai is about Family, with a capital F in case you didn't notice it, and halfway through I started quietly begging for it to be about something else, thank you. It does the one thing no movie should ever do: it makes us dread each successive scene. The core idea is not itself bad — a kid's flights of fantasy to help him cope with the changes imposed by having a younger sister — but the movie we get out of it is excruciating.
Mirai involves a young boy, maybe four or five years old, named Kun, whose mother has just given birth to a daughter. At first Kun is fascinated by the baby, Mirai (whose name means "future"). But then jealousy sets in: the baby gets all the attention, and all the time he used to have his with parents is siphoned off. This culminates in one of those domestic disasters where everyone ends up sobbing, and Kun runs off into their house's little in-ground garden.
Then the film throws a switch and drops Kun into a fantasy, where a mysterious, avuncular figure approaches him and tells him, "I used to be the prince of my house, too," before a baby came along and ruined everything. This, as Kun realizes, is the family dog, Yukko, also jealous of Kun's own attention, and there's a hilarious moment where Kun steals the dog's tail for his own and romps through the house.
Later, as Kun's jealousy continues to simmer, he falls into another fantasy. This time, he meets a teenaged girl who angrily calls him "big brother." Yes, this is his sister — the future version of his sister. She ha s the same birthmark on her hand as her younger self, and she also seems to need Kun to get her father to do ... certain things. On pain of being tickled. (Too bad Kun likes being tickled.) Does she really exist, or is she just a figment of Kun's imagination? Or is she a projection from the future into Kun's psyche? If so, why is it that when she appears, the younger Mirai vanishes?
This seems like fun at first. Then the movie starts to become less fun, or even clever, and then simply annoying and unendurable. Case in point: when Mirai first appears, she and Kun and Yukko (in his human incarnation) act out a seemingly endless sequence where Kun and the others have to put away a set of ceremonial dolls when Dad's not looking. This is, I guess, to allow Mirai's future to be improved in some way, but the scene goes on and on to the point of self-parody, until we just want it to be over. Much like, as we soon find, the movie itself.
A C- in life lessons
It gets worse. Every time Kun goes through another round of jealousy / resentment / tantrum, he's drawn into a flashback to another part of time: a flashback to his mother's past, his grandfather's life, and so on. The idea, I guess, is that these experiences teach Kun a Lesson In Empathy, but the lessons are so on the nose they become agonizing to sit through. Kid envies sister, kid gets a lesson from sister-out-of-time. Kid resents mom, kid gets a lesson from mom-out-of time. Kid hates dad for favoring Mirai ... you get the idea. What humor or wit there is in this setup is entirely situational; it's not extended to the whole story, which we learn to dread returning to.
It also doesn't help that the movie has a terribly claustrophobic flavor. The vast majority of the action takes place in the house, almost like a filmed version of a stage play with an elaborate set. (The house itself is an architectural marvel, so interesting by itself it deserves a better movie to exist in.) The few times we get out of the house, and into one of Kun's lush fantasies, it doesn't feel like the movie's expanding its horizons; it feels instead like a red herring, because we just know we're gonna end up back in that house before long. Worse, the lessons are themselves painfully shallow. They amount to little more than family photos coming to life and tut-tutting, that is when any function can be discerned at all.
While sitting through what felt like the thirteen thousandth hour of this movie, my mind began to wonder, possibly as a survival tactic. Given how Hosoda is one of the directors that's been described as a "next Miyazaki" (what a risible concept), how would someone like Miyazaki, or one of the other Ghibli cohorts, handle this material? For one, they would have found ways to make Kun's growth less of an ordeal for the audience. Think of how Mei from My Neighbor Totoro, arguably around the same age as Kun, was a delight to watch because of all the different and sensitive reactions she had to things. We couldn't wait to see what she did next. Kun has essentially a single attitude, that of immature grievance, and because the movie has made him the protagonist, it is straitjacketed into not being able to do much of anything with it. It just bangs on that one strident note over and over, until every time he opens his mouth we cover our ears.
Hosoda has made some movies I have loved (Wolf Children), some things I was less fond of but still appreciative of (Summer Wars), and some that seemed troubled at first but in time came together with surprising power (The Boy And The Beast). Mirai is easily the weakest of the bunch. I'm tempted to say it's the kind of movie only a parent could love, but most of the parents I know wouldn't want to sit through anything this smarmy. To say nothing of their kids.